Biomass pyrolysis refers to a thermochemical conversion technical method in which biomass is heated to 250-700° C. in the absence of an oxidant (air, oxygen, water vapor, etc.) or with limited oxygen, and macromolecular substances (lignin, cellulose, and hemicellulose) of the biomass are decomposed through thermochemical reactions into micromolecular fuel substances (solid charcoal, combustible gas, and bio-oil). Analyzed from the perspective of chemical reactions, the biomass is subjected to complex thermochemical reactions, including molecular bond breakage, isomerization, small molecule polymerization, and other reactions, in the process of pyrolysis. (Zhao Tinglin, Wang Peng, Deng Dajun, et al., Research Status and Prospect of Biomass Pyrolysis [J]. Renewable Energy Industry, 2007, 5: 54-60).
Products of biomass pyrolysis are combustible pyrolysis gas and solid biomass charcoal, both of which are products available for energy application. The gas not only is used as a fuel for heat supply, but also can be further reformed as a raw material for power generation and green liquid fuel synthesis. The biomass charcoal not only serves as a fuel, but also has many additional values: it is also used as a fuel for metal smelting, food and light industry, a reducing agent for electric furnace smelting, a covering agent in metal refining for protecting the metal from oxidation, and often a raw material for carbon disulfide and active carbon in chemical industry. Since the Chinese government prohibits making charcoal by burning wood, the biochar has a vast market now.
Chinese patent CN200910225125.3 discloses a helical pyrolysis reactor, including a shell. The shell is provided with a material inlet at the center of the top end, a phyrolysis gas outlet on the sidewall on the upper end, a heat carrier outlet on the sidewall on the lower end, and a charcoal powder outlet on the bottom. The material inlet of the pyrolysis reactor is located at the center of the top end.
Chinese patent CN01270113.0 discloses a continuously operating pyrolysis device for solid organics, mainly consisting of a helical conveyor reactor, a fluidized bed gasifier, a riser regenerator, a cyclone separator, a heat exchanger, a regenerant surge bin, etc. A material inlet of the pyrolysis device is located on the top end.
Chinese patent CN200920100781.6 discloses a biomass catalytic gasifier. A gasification reactor is of a vertical type. A helical feeder is disposed on the upper part of the gasification reactor. Multiple sets of heat conducting fins are mounted on an inner wall of the gasification reactor. A residue outlet and a water vapor outlet are respectively opened on the bottom of the gasification reactor. A water vapor distribution plate is disposed on the lower part of the gasification reactor. A gasification gas outlet is disposed on the top of the gasification reactor. The feeder of the device is disposed on the upper part of the gasification reactor.
To sum up, material inlets of current biomass pyrolysis reactors are located on the upper part or at the center of the upper part of the pyrolysis reactors. However, biomass fed from the upper part is stacked into nonuniform and uneven beds, and the biomass is easily bonded or bridged during the pyrolysis reaction, affecting flowing of the biomass material in the reactor. Empty bridging easily occurs, so that ash cannot be discharged normally, further blocking the reactor. Finally, the production cannot proceed continuously.
Due to the problem of conveying and the like, the existing biomass pyrolysis reactors cannot directly process biomass having a large size around 10 cm for continuous production. Moreover, in the existing pyrolysis reactors, ash falls through the gap between the grate and the inner wall of the reactor. However, the size of the gap is unscientific in actual production: if the size is large, the biomass raw material leaks out continuously; and if the size is small, blocking occurs easily, affecting the production.
It would be advantageous to overcome some of the disadvantages of the prior art.